Pulsed Dipolar EPR Spectroscopy and Metal Ions: Methodology and Biological Applications.

Pulsed dipolar electron paramagnetic resonance spectroscopy (PDS) is a valuable method for determining biomolecular structures and their conformational changes during function. Often, this method is applied to paramagnetic metal ions that are either intrinsic co-factors of biomolecules or introduced into biomolecules as spin labels. Here, the key achievements and the remaining challenges of PDS on metal ions are summarized and critically discussed. The first part of the Review describes the methodology of PDS experiments and the related data analysis for each of the biologically relevant paramagnetic metal centers. The second part highlights applications with the aim to give an idea about what kind of questions from structural biology can be answered by PDS-based distance measurements involving metal centers.